Touch detection device and display device having touch sensor function

ABSTRACT

A touch detection device includes: a detection surface; a plurality of sensor lines formed from a plurality of types of wiring lines having a different line capacitance; and a touch detection unit which detects an electric variation generated in a plurality of the sensor lines in response to touch or proximity of a detection target object to the detection surface, wherein the touch detection unit has an operational circuit for generating a detection signal representing the electric variation by performing an operation process using a line capacitance ratio for a plurality of outputs from a plurality of types of the sensor lines neighboring to one another with a different line capacitance.

The subject matter of application Ser. No. 12/791,667 is incorporatedherein by reference. The present application is a Continuation of U.S.Ser. No. 12/791,667, filed Jun. 1, 2010, which claims priority toJapanese Patent Application No. JP 2009-155188 filed in the JapanesePatent Office on Jun. 30, 2009, the entire content of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a touch detection device for detectingtouch or proximity of a user's finger or a pen to a detection surface.In addition, the present invention relates to a display device having afunction of the touch detection device (touch sensor).

2. Description of the Related Art

In general, a touch detection device is a device for detecting touch orproximity of a user's finger or a pen to a detection surface.

A display device is known in the art, which allows a user to inputinformation instead of typical buttons by overlappingly forming a touchdetection device called a touch panel on a display panel and displayingvarious buttons as an image on a display surface. When such a displaydevice is applied to a small-sized mobile device, it is possible toobtain various advantages such as a large screen, saving space for amanipulation unit, reduction of components because a display and anarrangement of buttons can be integrated together. As such, generallyspeaking, the “touch panel” refers to a touch detection device having apanel shape combined with a display device.

It is known that three touch detection types of the touch panel includean optical type, a resistive film type, and an electrostatic capacitancetype. Meanwhile, in order to associate an electric variation generatedby touch or proximity with positional information, a plurality of wiringlines arranged in a matrix shape combined to determine the position aredemanded.

The thickness of the entire display device (e.g., a liquid crystalmodule) increases when the touch panel is mounted. Particularly, when itis employed in a mobile device, a protection layer for preventingscratches on the touch panel is additionally demanded, thereby furtherincreasing the thickness of the liquid crystal module. This is against aminiaturization trend.

In this regard, for example, Japanese Unexamined Patent ApplicationPublication No. 2008-9750 discloses a touch panel conductive filminterposed between a viewer's side panel of the liquid crystal displaydevice and a viewer's side polarization plate disposed in the outersurface thereof. Japanese Unexamined Patent Application Publication No.2008-9750 proposes a liquid crystal display device having anelectrostatic capacitance type touch panel using an external surface ofthe polarization plate as a touch surface between the touch panelconductive film and the external surface of the polarization plate inorder to obtain a thin thickness.

SUMMARY OF THE INVENTION

However, the aforementioned touch panel (touch detection device) or thedisplay device having a touch sensor function has the followingdisadvantages.

The touch detection device generates an electric variation on the sensorline in response to touch or detection of a detection target object(such as a user's finger or a stylus pen) to the detection surfacewithout distinction of an optical type, a resistive film type, and anelectrostatic capacitance type. Such an electric variation in the sensorline is detected in a leading end of the sensor line extending to theouter side from the detection surface. However, since the touchdetection device generally demands a plurality of wiring lines inaddition to the sensor line, the signal-to-noise (S/N) ratio of thedetection signal decreases when the electric potential fluctuation inthis wiring lines is overlapped on the sensor line as noise. A pixelcircuit usually has an amplification function in an optical type, and anelectric variation is relatively large in the resistive film type. Onthe contrary, in an electrostatic capacitance type touch detectiondevice, the electric variation on the sensor line has a relatively smallamplitude, and prevention of degradation of the S/N ratio of thedetection signal is important, particularly, in the electrostaticcapacitance type touch detection device.

Meanwhile, the display device having a touch sensor function makesprogress from simply attaching a touch panel to the external surface ofthe display panel to forming an electrode for driving the touch sensorinside the display panel to achieve new objectives such as a thinnerthickness and cost reduction. Therefore, a wiring line having a largevoltage fluctuation functioning as noise source to the sensor line isfrequently disposed in proximity of the sensor line in a thicknessdirection of the panel. Therefore, prevention of degradation in the S/Nratio of the detection signal becomes more important in the displaydevice having a touch sensor function. Although this is a frequent casewithout distinction of the optical type, the resistive film type, or theelectrostatic capacitance type, noise reduction in the sensor line ishighly demanded particularly in the electrostatic capacitance type dueto the aforementioned reason.

It is desirable to remove a noise component from the detection signalobtained by detecting an electric variation in the sensor line in atouch detection device and a display device having a touch sensorfunction.

According to an embodiment of the present invention, there is provided atouch detection device including a detection surface, a plurality ofsensor lines formed from a plurality of types of wiring lines having adifferent line capacitance, and a touch detection unit.

The touch detection unit detects an electric variation generated in aplurality of the sensor lines in response to touch or proximity of adetection target object to the detection surface. In addition, the touchdetection unit has an operational circuit for generating a detectionsignal representing the electric variation by performing an operationprocess using a line capacitance ratio for a plurality of outputs from aplurality of types of the sensor lines neighboring to one another with adifferent line capacitance.

It is preferable that a plurality of the sensor lines are formed from aplurality of M types of wiring lines that have a different length foreach type and are arranged in parallel to one another, and M sensorlines neighboring to one another have a different type. It is preferablethat the touch detection unit has the operational circuit provided foreach of the M sensor lines that neighbor to one another and have adifferent type. The operational circuit may have a selector mechanismfor sharing between sensor lines.

According to an embodiment of the present invention, the M sensor linesare formed from wiring lines having, the same material, the samethickness, the same width, and a plurality of different types oflengths. In this case, it is preferable that each of the M sensor lineshas a length which is a K multiple (where, K=1 to N) of a length L of anelementary sensor line having a shortest length. It is preferable thatthe operational circuit obtains the detection signal by selecting twosensor lines from the M sensor lines, obtaining a difference of outputsof the two selected sensor lines of which a ratio of lengths is set to k(where, k is a natural number equal to or larger than 2), and removingthe obtained difference with (k−1).

According ton an embodiment of the present invention, the touchdetection device generates an electric variation on a plurality of thesensor lines in response to touch or proximity of a detection targetobject (such as a user's finger or a stylus pen) to the detectionsurface. Typically, since the detection surface is larger than thedetection target object, the electric variation is generated in severalof a plurality of sensor lines. The sensor line where the electricvariation is generated is formed from a plurality of types of wiringlines having a different line capacitance. Therefore, in each sensorline where the electric variation is generated, the electric variationis transmitted to several sensor lines having a different linecapacitance and input to the touch detection unit.

The touch detection unit includes an operation circuit. The operationalcircuit receives a plurality of inputs from a plurality of types ofsensor lines that have a different line capacitance and neighbor to oneanother to perform an operational process. In this operational process,a line capacitance ratio is used, and thus, the detection signalrepresenting the electric variation generated in response to touch orproximity to the detection surface is generated from the operationalcircuit. The detection signal output from the operational circuit isused to detect presence/absence of the detection target object or aposition on the detection surface.

According to an embodiment of the present invention, the display devicehaving a touch sensor function includes a display surface, a pluralityof image signal lines, a display function layer, a plurality of sensorlines, and a touch detection unit.

The display function layer changes display of the display surface inresponse to a voltage applied to a plurality of the image signal lines.

The touch detection unit detects an electric variation generated from aplurality of the sensor lines in response to touch or proximity of thedetection target object to the detection surface. In addition, the touchdetection unit includes an operational circuit for generating adetection signal representing the electric variation by performing anoperation process using a line capacitance ratio for a plurality ofoutputs from a plurality of types of sensor lines that neighbor to oneanother and have a different line capacitance.

According to an embodiment of the present invention, the display devicehaving a touch sensor function includes a plurality of pixels aplurality of pixel electrodes, m opposite electrodes, a plurality ofsensing electrodes, a display function layer, a write driving scanningunit, an AC driving scanning unit, and a touch detection unit.

A plurality of the pixels are connected to one another by a plurality ofscanning lines and a plurality of image signal lines, and each of thepixels has a switch for writing a voltage of corresponding one of theimage signal line in response to a voltage applied to corresponding oneof the scanning lines.

A plurality of pixel electrodes are provided for each pixel and arrangedin a matrix in a planar shape.

The m opposite electrodes are arranged in a planar shape opposite to thepixel electrode, have a pitch length one or more times a pitch length ofan arrangement of the pixel electrodes in a scanning direction which isan arrangement direction of one side of the pixel electrode, and arearranged with the same interval in the scanning direction.

A plurality of the sensing electrodes have an electrostatic capacitancebetween each of the m opposite electrodes. A plurality of the sensingelectrodes are formed from a plurality of types of wiring lines having adifference line capacitance.

The display function layer provides an image display function inresponse to a signal voltage applied between the pixel electrode and theopposite electrode that face to each other.

The write driving scanning unit performs a write operation for writingvoltages of a predetermined number of the image signal lines by turningon a predetermined number switches for a predetermined number of thepixel electrodes lined up in the other direction perpendicular to thescanning direction. The write driving scanning unit performs a writeoperation and repeats a shift operation that sequentially switches apredetermined number of pixel electrodes, which is a write target, inthe scanning direction.

The AC driving scanning unit drives, with an AC voltage, s oppositeelectrodes (where, 1≦s<n) defined from the m opposite electrodes under acondition that opposite electrodes opposite to a predetermined number ofthe pixel electrodes as a write target are included. In addition, the ACdriving scanning unit shifts the s opposite electrodes as an AC drivingtarget in the scanning direction to satisfy the aforementionedcondition.

The touch detection unit detects a variation in a voltage applied to theelectrostatic capacitance caused by an external capacitance in the sideof the sensing electrode. In addition, the touch detection unit includesan operational circuit for generating a detection signal representing avariation in a voltage applied to the electrostatic capacitance byperforming an operation process using a line capacitance ratio for aplurality of outputs from a plurality of types of the sensing electrodesthat have a different line capacitance and neighbor to one another.

In the two display device having the aforementioned configurationaccording to an embodiment of the present invention, a plurality of thesensor lines (or sensing electrodes) and the touch detection unit havethe same function as that of the aforementioned touch detection device(However, the surface where the detection target object touches or islocated in proximity is sometimes referred to as a display surface inthe corresponding display device).

The display function layer may neighbor to a plurality of the sensorlines (or a plurality of the sensing electrodes), for example, in athickness direction of the display device. In this case, a plurality ofimage signal lines providing a voltage for driving the display functionlayer also neighbor to a plurality of the sensor lines. Particularly,the image signal lines may extend in the same direction as that of aplurality of the sensor lines (or a plurality of the sensingelectrodes). In this case, each of a plurality of sensor lines (or aplurality of sensing electrodes) is influenced by an electric potentialvariation several neighboring image signal lines, and the electricpotentials thereof fluctuate.

In the display device according to an embodiment of the presentinvention, the operational circuit performs an operation process using aline capacitance ratio for a plurality of outputs from a plurality oftypes of the sensor lines (or the sensing electrodes) that have adifferent line capacitance and neighbor to one another. As a result, theelectric potential fluctuation component generated by the effect of theaforementioned other wiring lines (e.g., image signal lines) iseffectively removed from the detection signal output from theoperational circuit.

According to embodiments of the present invention, it is possible toprovide a touch detection device capable of removing a noise componentfrom the detection signal obtained by detecting an electric variation inthe sensor lines. In addition, it is possible to provide a displaydevice capable of removing from the detection signal a noise componentthat changes a voltage applied to the electrostatic capacitance of thesensor line (or the sensing electrode).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are an equivalent circuit diagram and a schematiccross-sectional diagram illustrating operations of the touch sensor unitaccording to first to third embodiments of the present invention.

FIGS. 2A and 2B are an equivalent circuit diagram and a schematiccross-sectional diagram when a finger touches or is in proximity of thetouch sensor unit of FIG. 1.

FIGS. 3A to 3C illustrate input/output waveforms of the touch sensorunit according to an embodiment of the present invention.

FIGS. 4A and 4B are a top plan view and a schematic cross-sectional viewillustrating a configuration of the touch detection device according tofirst and second embodiments of the present invention.

FIGS. 5A to 5C are a top plan view, an equivalent circuit diagram, andan equation illustrating touch sensor detection according to first tothird embodiment of the present invention.

FIGS. 6A to 6C are a waveform diagram of the long sensor output and theshort sensor output, a schematic diagram of components, and anoperational example.

FIGS. 7A and 7B illustrate a border position in the touch detectiondevice according to a first embodiment of the present invention and anoperation course or an operation result.

FIGS. 8A and 8B illustrate a diagram illustrating a border scan positionand an exemplary circuit diagram of the AC signaling source and theoperation circuit.

FIGS. 9A to 9C are schematic diagrams illustrating components of thesensor line outputs according to a second embodiment of the presentinvention.

FIGS. 10A and 10B are a diagram illustrating a border position in thetouch detection device according to a second embodiment of the presentinvention and a table showing an operation course and an operationresult.

FIGS. 11A to 11D are top plan views and a schematic cross-sectional viewillustrating an electrode pattern for touch detection of the displaydevice according to a third embodiment of the present invention andconnection with the driving circuit.

FIG. 12 is an equivalent circuit diagram of the pixel circuit of thedisplay device according to a third embodiment of the present invention.

FIGS. 13A to 13C illustrate a border scanning performed by the displaydevice according to a third embodiment of the present invention.

FIG. 14 is an enlarged plan view illustrating a liquid crystal displayunit after forming the pixel electrode in the display device accordingto a third embodiment of the present invention.

FIG. 15 is a schematic cross-sectional view illustrating a configurationexample according to a fifth modification.

FIG. 16 is a schematic cross-sectional view illustrating a configurationexample according to a sixth modification.

FIG. 17 is a schematic cross-sectional view illustrating a configurationexample according to a seventh modification.

FIG. 18 is a top plan view illustrating a sensor line arrangementaccording to an eighth modification.

FIG. 19 is a top plan view illustrating a sensor line arrangementaccording to a ninth modification.

FIG. 20 is a top plan view illustrating a sensor line arrangementaccording to a tenth modification.

FIG. 21 is a top plan view illustrating another sensor line arrangementaccording to a tenth modification.

FIG. 22 is a top plan view illustrating a sensor line arrangementaccording to an eleventh modification.

FIGS. 23A and 23B are waveform diagrams illustrating a noise source.

FIGS. 24A1 to 24B3 are waveform diagrams illustrating a noisesuppression effect.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings by exemplifying an electrostaticcapacitance type touch sensor and a liquid crystal display device havinga touch detection function. In addition, the embodiments of the presentinvention are applicable to a resistive film type or optical type touchsensor as well. While a liquid crystal display device is describedherein the embodiments of, the present invention are applicable to otherdisplay devices such as an organic electroluminescence (EL) displaydevice.

The descriptions will be made in the following sequence.

1. First Embodiment: a touch detection device performing an operationalprocess using outputs from double sensor lines

2. First Modification: a case where only the width of the sensor line isdifferent

3. Second Modification: a case where the length and the width of thesensor lines are different (line capacity ratio Kc=2)

4. Third Modification: a case where the length and the width of thesensor lines are different (line capacity ratio Kc≠2)

5. Second Embodiment: a touch detection performing an operationalprocess using outputs from three sensor lines

6. Third Embodiment: a display device performing border scanning

7. Fourth Modification: a matrix arrangement of sensor lines

8. Fifth to Seventh Modifications: a structural example of a liquidcrystal display device in a horizontal electric field mode

9. Eighth Modification: an extremely-short sensor line

10. Ninth Modification: arbitrarity of the arrangement sequence ofsensor lines

11. Tenth Modification: sharing of sensor lines using an operationalcircuit

12. Eleventh Modification: a shield layer

13. Noise Sources in Display Devices and Noise Suppression Effect

14. Other Effects

1. First Embodiment Basic Configuration and Operations for Touch-Sensing

First, fundamentals of electrostatic capacitance element typetouch-sensing will be described with reference to FIGS. 1A to 3C asassumptions of the first embodiment (common to other embodiments).

FIGS. 1A and 2A are equivalent circuit diagrams illustrating a touchsensor unit, and FIGS. 1B and 2B are constructional diagrams (schematiccross-sectional views) illustrating a touch sensor unit. Here, FIGS. 1Aand 1B illustrate a case where a finger as a sensing target object isnot in proximity of the sensor, and FIGS. 2A and 2B illustrate a casewhere a finger is disposed in proximity of or touches the sensor.

The illustrated touch sensor unit is an electrostatic capacitance typetouch sensor and includes capacitance elements as shown in FIGS. 1B and2B. Specifically, a capacitance element (electrostatic capacitanceelement) C1 includes a dielectric body D and a pair of electrodesarranged to face each other with the dielectric body D being interposedtherebetween, i.e., the driving electrode E1 and the detection electrodeE2. As shown in FIGS. 1A and 2A, the driving electrode E1 of thecapacitance element C1 is connected to the AC signaling source AS whichgenerates an AC pulse signal Sg. The detection electrode E2 of thecapacitance element C1 is connected to the operational circuit 8A. Inthis case, the detection electrode E2 is grounded via a resistor R sothat the DC level is electrically fixed.

An AC pulse signal Sg having a predetermined frequency of, for example,several kHz to several tens of kHz is applied from the AC signalingsource AS to the driving electrode E1.

A waveform diagram of the AC pulse signal Sg is illustrated in FIG. 3B.In response to applying the AC pulse signal Sg, a signal (detectionsignal Vdet) having an output waveform shown in FIG. 3A is generated inthe detection electrode E2.

As will be described in detail in another embodiment below, in a liquidcrystal display device having a function of the touch sensor within aliquid crystal display panel, the driving electrode E1 corresponds to anopposite electrode (common electrode for a plurality of pixels facingthe pixel electrode) for driving liquid crystals. Here, the oppositeelectrode is subjected to an AC driving, a so-called Vcom-driving fordriving liquid crystals. Therefore, according to an embodiment of thepresent invention, a common driving signal for driving Vcom is generatedfrom a plurality of positions at a timing different from that displayedor simultaneously and also used as an AC pulse signal Sg for driving thedriving electrode E1 for the touch sensor.

In the state shown in FIGS. 1A and 1B in which a finger is not touched,the driving electrode E1 of the capacitance element C1 is driven with anAC voltage, and an AC detection signal Vdet is generated in thedetection electrode E2 depending on charge/discharge operations. Here, adetection signal thereupon is denoted by an “initial detection signalVdet0.” Since the detection electrode E2 side is grounded from theviewpoint of a DC voltage, but is not grounded from the viewpoint of ahigh frequency domain, a path for discharging the AC voltage is notprovided, and the pulse crest value of the initial detection signalVdet0 is relatively large. However, after the AC pulse signal Sg rises,and time elapses, the pulse crest value of the initial detection signalVdet0 gradually falls down due to a loss. FIG. 3C exaggeratedly shows awaveform with a scaling factor. The pulse crest value of the initialdetection signal Vdet0 decreases from an initial value of 2.8 V to 0.5 Vdue to a high frequency loss as some time elapses.

In addition, the waveform of FIG. 3C has no noise, and the waveformhaving noise and noise rejection will be described later.

From this initial state, as a finger touches or approaches to thedetection electrode E2 within an effective point-blank distance, thecircuit state changes to be equivalent to a case where the capacitanceelement C2 is connected to the detection electrode E2 as shown in FIG.2A. This is because a human body is equivalent to a capacitance elementof which one side is grounded from the viewpoint of a high frequencydomain. In this contact state, a discharge path for the AC signal isformed through the capacitance elements C1 and C2. Therefore,accompanying with charge/discharge of the capacitance element C1 and C2,AC currents I1 and I2 flows through the capacitance elements C1 and C2,respectively. For this reason, the initial detection signal Vdet0 isvoltage-divided according to the unequally defined values of thecapacitance elements C1 and C2, and the pulse crest value decreases.

The detection signal Vdet1 shown in FIGS. 3A and 3C are detectionsignals generated in the detection electrode E2 when a finger touches.Referring to FIG. 3C, it is recognized that the attenuation amount ofthe detection signal is 0.5 to 0.8 V. The operational circuit 8A shownin FIGS. 1A to 2B detects the attenuation of the detection signal, forexample, using a threshold value Vt to detect touch of a finger.

[Schematic Configuration of Touch Detection Device]

FIG. 4A is a schematic top plan view illustrating a touch detectiondevice according to an embodiment of the present invention, in which theinner side of the device is penetrated from the detection surface (thesurface of the protection layer) by removing the outermost surface ofthe protection layer. In addition, FIG. 4B is a schematiccross-sectional view along the line IVB-IVB of FIG. 4A.

As shown in FIG. 4B, the touch detection device 10 has a drivingelectrode DEm between the first and second substrates 11 and 12. Thesurface opposite to the driving electrode DEm side of the secondsubstrate 12, i.e., the surface of the detection surface side, isprovided with sensor lines.

As shown in FIG. 4A, the sensor line includes a plurality of lineshaving two types of lengths extending in a y-direction. Hereinafter, therelatively long sensor line is referred to as “a long sensor line LSL,”and the relatively short sensor line is referred to as “a short sensorline SSL.” In this example, the long sensor lines LSLi (i=1, 2, 3, . . ., n) and the short sensor lines SSLi (i=1, 2, 3, . . . , n) arealternately arranged along an x-direction. Although will be described indetail below, a sensor line output is operated for each pair of theneighboring sensor lines having different lengths, i.e., a pair of thelong sensor line LSLi and the short sensor line SSLi. In this example,the length of the long sensor line LSLi is a double of the length of theshort sensor line SSLi.

Hereinafter, the n long sensor lines LSLi and the n short sensor linesSSLi are collectively called “2n sensor lines SL.”

As shown in FIG. 4A, the m driving electrodes having a band shape andextending in an x-direction are arranged with the same pitch in ay-direction. For example, the m driving electrodes DEj (j=1, 2, 3, . . ., m) are perpendicular to 2n sensor lines SL(LSL+SSL).

Materials of the first and second substrates 11 and 12 are notparticularly limited. However, 2n sensor lines SL is demanded to becapacitively coupled to m driving electrodes DEm, respectively. For thisreason, the thickness or the material of the second substrate 12 isdefined such that the corresponding capacitive coupling has apredetermined strength. From this viewpoint, the second substrate 12 maybe omitted, and an insulator may be interposed between the 2n sensorlines SL and the m driving electrodes DEm.

A scan driving unit 9 is connected to one side end of the m drivingelectrodes DEj. In addition, a touch detection unit 8 is connected toone side end of the 2n sensor lines SL (LSL+SSL).

The scan driving unit 9 has AC signaling sources AS for each drivingelectrode (refer to FIGS. 1A to 2B). The activated AC signaling sourcesAS are sequentially switched in a direction (a scanning direction)represented by an arrow within the block of the scan driving unit 9 ofFIG. 4A. Alternatively, the scan driving unit 9 may have a single ACsignaling source AS, so that connection between the single AC signalingsource AS and one DEj of the m driving electrodes DE1 to DEm issequentially switched in a scan direction.

As such, the operation of switching the driving electrode receiving theAC signal in practice from one side end to the other side end of the mdriving electrodes is called a “scan.”

In addition, the function and configuration of the touch detection unit8 will be described below.

In the present embodiment, a perpendicular arrangement between thedriving electrodes and the sensor lines is dispensable, but the shapesor arrangements of each of the sensor lines and each of drivingelectrodes may be not particularly limited as long as a capacitivecoupling therebetween is uniform or nearly uniform within the detectionsurface.

However, as shown in FIG. 4A, the arrangement of the touch detectionunit 8 and he scan driving unit 9 may be readily performed by extractingthe sensor lines from one of two perpendicular sides of the detectionsurface and connecting them to the touch detection unit 8 as well as byextracting the driving electrodes from the other side of the twoperpendicular sides and connecting them to the scan driving unit 9.Therefore, the perpendicular arrangement between the driving electrodesand the sensor lines is preferable, but the invention is not necessarilylimited thereto.

[Signal Component of Detection Signal]

FIG. 5A illustrate a case where the AC signaling source AS drives thefirst driving electrode DE1 of the m driving electrodes DEj. Inaddition, FIG. 5B illustrates an equivalent circuit diagram of a touchsensor when an arbitrary single user's finger is in proximity of one ofthe n long sensor lines LSLi of FIG. 4A at that moment.

As shown in FIG. 5A, the AC signaling source AS is connected to thedriving electrode DE1 to drive the driving electrode DE1 with an ACvoltage. In this case, the touch sensor is represented as an equivalentcircuit shown in FIG. 5B. However, here, each electrostatic capacitanceof the capacitance elements C1_1 to C1_m is referred to as “Cp”, acapacitance element (a parasitic capacitance) connected in addition tothe capacitance elements C1_1 to C1_m is referred to as “Cc”, and aneffective value of the AC voltage from the AC signaling source AS isreferred to as “V1”. In this case, the detection signal Vdet detectedfrom the touch detection unit 8 (refer to FIG. 4A) becomes a voltage Vswhen a finger does not touch and Vf(<Vs) when a finger touches. In arelationship with FIG. 3, the voltage Vs corresponds to the “initialdetection signal Vdet0,” and the voltage Vf corresponds to the“detection signal Vdet1.” Hereinafter, the voltages Vs and Vf arereferred to as sensor voltages.

The sensor voltage Vs in the untouched state is represented as theequation of FIG. 5C. Based on this equation, as the number m of thedriving electrodes DE increases, the electrostatic capacitance value Cpdecreases accordingly. Therefore, the “mCp” in the denominator in theequation of FIG. 5C becomes nearly constant. In addition, the parasiticcapacitance Cc is slightly affected by the number m of the drivingelectrodes DE, but may be considered nearly constant. For this reason,the remainder of the numerator of the equation of FIG. 5C does notsignificantly change, but the numerator decreases. Therefore, as thenumber m of the driving electrodes DE increases, the magnitude of thesensor voltage Vs (the crest value of the detection signal in theuntouched state) also decreases. Meanwhile, similar to the sensorvoltage Vs, the sensor voltage Vf (the crest value of the detectionsignal in the touched state) is inversely proportional to “mCp” andproportional to “Cp.” This is because the external capacitance C2 addedby proximity of a finger is remarkably smaller than the electrostaticcapacitance Cp.

Consequently, as the number m of the driving electrodes DE increases,the crest value of the detection signal increases.

On the contrary, if the number m of the driving electrodes DE is small,and the area of a single driving electrode DE1 is large, the crest valueof the detection signal increases, but the resolution (a minimumrecognizable size of the detection target object) for detecting the sizeof the detection target object decreases. In addition, accuracy ofposition detection for detecting the position of the detection targetobject also increases as the number m decreases. Therefore, if theaccuracy for detecting the size or the position of the object increasesfor high performance, the area of a single driving electrode DE isinevitably reduced. However, as described above, if the number m of thedriving electrodes DE increases, and the area of the electrodedecreases, the crest value of the detection signal of the touch sensordecreases.

In this example, the electrostatic capacitance Cp at the intersection ofthe driving electrode DE varies depending on the area of the singledriving electrode DE. In other words, as the area (particularly, width)of the driving electrode DE increases, the electrostatic capacitance Cpincreases accordingly. In addition, as the area (particularly, thewidth) of the single sensor line SLi increases, the electrostaticcapacitance Cp accordingly increases.

However, if there is noise in the sensor line SLi, the signal component(an average crest value of the sensor voltages Vs and Vf) decreases incomparison with the noise component of the detection signal Vdet.Therefore, the S/N ratio of the detection signal Vdet decreases. The S/Nratio decreases as the number m of the driving electrodes DE increases,and the width of the single driving electrode DE decreases. In addition,as the magnitude of the noise component (the amount of noise) approachesto the signal component, it is difficult to apply noise separationtechnologies. Particularly, if the noise component periodicallyfluctuates, and the period thereof is close to the period of thedetection signal, it is further difficult to separate the noise.

Since there is a tradeoff between the sensitivity (the resolution of thesize of the detection object or the position detection accuracy) of thetouch sensor and the S/N ratio of the detection signal Vdet, it isdifficult to improve both properties even when the noise separationtechnology such as a noise filter is applied.

FIGS. 5A and 5B illustrate a case where the intersection between thefirst driving electrode DE and the long sensor line LSLi is operated,but is similarly used to describe a case of driving the short sensorline SSLi here.

Since the long sensor lines LSLi (refer to FIG. 4A) intersect with allof the m driving electrodes DE, the denominator of the equation of FIG.5C also becomes “mCp+Cc” in this case. On the contrary, the number ofintersections between the short sensor lines SSLi and the drivingelectrodes DE (refer to FIG. 4A) is approximately a half of the numberof intersections between the long sensor lines LSLi and the drivingelectrodes DE. Therefore, the denominator of the equation of FIG. 5Cbecomes “mCp/2+Cc.” Here, it is assumed that the parasitic capacitanceCc is sufficiently smaller than a total coupling capacitance, i.e.,“mCp” or “mCp/2.” Under this assumption, the signal component (anaverage crest value of the sensor voltages Vs and Vf) of the detectionsignal Vdet output from the short sensor line SSLi becomes approximatelya double of that of the long sensor line LSLi.

In addition, the fact that the signal component of the detection signalVdet of the short sensor line becomes a double of that of the longsensor line is concluded under the assumption (hereinafter, referred toas a first assumption) that the parasitic capacitance Cc is sufficientlysmaller than the total coupling capacitance (mCp, mCp/2).

On the contrary, it is assumed that the parasitic capacitance Cc of eachsensor line is sufficiently larger than the total coupling capacitance(mCp, mCp/2) (hereinafter, referred to as a second assumption). Underthe second assumption, while the parasitic capacitance Cc is dominatedin the denominator of the equation of FIG. 5C, the parasitic capacitanceCc is proportional to the line capacitance and thus, decreases as theline capacitance decreases. That is, the parasitic capacitance Cc of theshort sensor line is nearly halved from the parasitic capacitance Cc ofthe long sensor line. Therefore, the conclusion that the signalcomponent of the detection signal Vdet of the short sensor line becomesa double of that of the long sensor line is also similarly extractedfrom the second assumption.

Meanwhile, a halfway assumption between the first and secondassumptions, i.e., a case that either the total coupling capacitance(mCp, mCp/2) of the denominator of the equation of FIG. 5C or theparasitic capacitance element Cc is not negligible will be described (athird assumption). Also in this case, it is possible to readily inferthat the denominator of the equation of FIG. 5C of the short sensor lineis a half of that of the long sensor line, and the conclusion does notchange.

Consequently, if the length of the short sensor line is set to a half(½) of the length of the long sensor line, the signal component of theshort sensor line becomes a double of that of the long sensor line. Thisis also obtained under the assumption that the long and short sensorlines are formed in the wiring layer having the same width, the samethickness, and the same material.

Generally, if the wiring layer has the same thickness and the samematerial, the line capacitance is proportional to the length. Therefore,generally speaking, it could be said that, if the long and short sensorlines have the same width, the same thickness, and the same material,the ratio of the length nearly corresponds with the line capacitanceratio Kc, and the magnitude (the crest value) of the signal component ofthe detection signal is defined to be nearly inversely proportional tothe line capacitance ratio Kc.

According to an embodiment of the present invention, the linecapacitance includes a coupling capacitance with other conductiveportions and the parasitic capacitance in addition to the capacitance ofthe wiring layer itself.

2. First Modification

Here, another embodiment (modification) of changing the line capacitanceratio Kc will be described.

In the first modification, both the sensor lines have the same length,the same thickness, and the same material, but the width is different.

For example, a second sensor line having a width doubled by the firstsensor line is considered. In this case, the line capacitance ratio Kcof the second sensor line against the first sensor line is approximately2, and the denominator of the equation of FIG. 5C of the second sensorline becomes approximately a double of that of the first sensor line. Inthis case, if the widths of the m driving electrodes DEj are constant,the electrostatic capacitance Cp of the second sensor line becomes adouble of that of the first sensor line. Therefore, in the firstmodification, the signal component (the crest value) of the detectionsignal becomes nearly the same between the first and second sensorlines.

3. Second Modification

In the second modification, both the sensor lines have the samethickness and material, but the length and the width are different.

For example, as shown in FIGS. 4A and 4B, it is assumed that the lengthof the short sensor line is a half (½) of the length of the long sensorline, and the width of the short sensor line is a half (½) of the widthof the long sensor line. In this case, the denominator of the equationof FIG. 5C of the short sensor line becomes a quarter (¼) of that of thelong sensor line (the line capacitance ratio Kc is 4 or ¼). In addition,the electrostatic capacitance Cp of the short sensor line becomesapproximately a half (½) of that of the long sensor line. Therefore, inthe second modification, the signal component (the crest value) of thedetection signal output from the short sensor line becomes approximatelya double of the signal component (the crest value) of the detectionsignal output from the long sensor line.

4. Third Modification

In the third modification, similar to the second modification, both thesensor lines have the same thickness and the same material, but thelength and the width are different.

However, it is assumed that, the length of the short sensor line is ahalf of the length of the long sensor line as shown in FIGS. 4A and 4B,but the width of the short sensor line is a double of the width of thelong sensor line. In this case, the denominator of the equation of FIG.5C does not change between the short sensor line and the long sensorline (the line capacitance ratio Kc is 1). In addition, theelectrostatic capacitance Cp of the short sensor line becomesapproximately a double of that of the long sensor line. Therefore, inthe third modification, the signal component (the crest value) of thedetection signal output from the short sensor line is approximately adouble of that of the signal component (the crest value) of thedetection signal output from the long sensor line.

In FIGS. 4A and 4B, in the first to third modifications, a scalingfactor was set to 2 by changing only the length, only the width, or boththe length and the width of one of the sensor lines with respect to theother sensor line. However, the scaling factor may be 3 or any othernatural number. As a result, it is possible to change the signalcomponent of detection signal of one of the sensor lines with respect tothe signal component of the detection signal of the other sensor line asmuch as double, triple, or any natural number of times.

Inversely speaking, this means the signal component of the detectionsignal of one sensor line varies with respect to the signal component ofthe detection signal of the other sensor line as much as the same, ahalf, one-third, . . . , or an inverse of any natural number of times.

In FIGS. 4A and 4B, in the first to third modifications, while at leastone of the length and the width changes, a parameter for changing theline capacitance ratio Kc is also associated with the material and thethickness of the wiring layer in addition to the length and the width.Therefore, the line capacitance ratio Kc may change between both thesensor lines by changing only the material or the thickness of thewiring layer for forming the sensor lines or combining them with otherparameters.

[Noise Component]

The noise component is differently superimposed on the sensor linesdepending on the noise source assumption.

The touch detection device itself may be made thinner with highperformance and may be mounted on another electronic device (forexample, a display device illustrated in the embodiment describedbelow). Therefore, other lines at which an electric potential fluctuatesmay be arranged under the sensor lines of the touch detection device,and the distance between the sensor lines and those other lines tends todecrease as the touch detection device is made thinner.

When a wiring line, where an electric potential fluctuates, as a noisesource is arranged in parallel with the sensor line, the magnitude ofthe noise component (noise amount) is defined by a strength of thecapacitive coupling as a main parameter associated with the length andthe width as well as a thickness or a material thereof.

Here, since noise is superimposed on the sensor line through a parasiticcapacitance Cc, the noise amount increases as the parasitic capacitanceCc increases. However, as described above, since the parasiticcapacitance Cc is proportional to the line capacitance, it is alsoenvisaged that the noise amount increases as the line capacitanceincreases from this viewpoint. On the other hand, as the linecapacitance of the sensor line increases, a variation of the electricalpotential on the sensor line is hardly generated by the noise. For thisreason, even when the line capacitance ratio Kc changes, the noiseamount hardly changes.

For example, in a case where the width of the sensor line is equal, andthe length is halved (line capacitance ratio Kc=2 or ½), the linecapacitance (electrostatic capacitance Cp) is halved as the length ishalved, and the parasitic capacitance Cc is accordingly halved. For thisreason, even when the length of the sensor line changes, the noiseamount hardly changes.

In a case where the length of the sensor line is equal, and the width ishalved (line capacitance ratio Kc=2 or ½), the line capacitance(electrostatic capacitance Cp) is halved as the width is halved, and theparasitic capacitance Cc is halved accordingly. For this reason, evenwhen the width of the sensor line changes, the noise amount hardlychanges.

Meanwhile, in a case where the wiring line of the noise source traversesthe width direction of the sensor line, the magnitude of the noisecomponent is defined by a strength of the capacitive coupling as a mainparameter associated with the width as well as a thickness or a materialthereof. Even in this case, since the noise is superimposed on thesensor line via the parasitic capacitance Cc, it is envisaged that theparasitic capacitance Cc increases as the line capacitance increases asdescribed above. However, since the line capacitance increases as thewidth increases, a variation of the electrical potential of the sensorline is hardly generated by the noise, and also in this case, the noiseamount hardly changes even when the line capacitance ratio Kc changes.For example, in a case where the wiring lines traversing the long sensorline LSLi and the short sensor line SSLi having the same width as shownin FIGS. 4A and 4B function as a noise source, the noise componentshaving the same strength are superimposed on these two sensor lines.

The noise source may be incoming electromagnetic waves from the outerside. In this case, the sensor line functions as an antenna forgenerating noise.

In this case, the magnitude of the noise component is defined by astrength of the capacitive coupling as a main parameter associated witha length or a width as well as a thickness or a material thereof. Inthis case, since the noise superimposed on the sensor line does notinclude a parasitic capacitance Cc, the noise component tends to beproportional to the line capacitance. Therefore, in this case, theincoming noise amount depends on the line capacitance ratio Kc.

Based on the descriptions above, while some types of noise sources maybe associated with the line capacitance ratio Kc (e.g., incoming noise),it could be assumed that, when a wiring line having a fluctuatingelectric potential is in proximity of the sensor line, inductive noisefrom this wiring line is dominant, and the proportion of the incomingnoise against the entire noise amount is negligible. Therefore, theaccuracy of a noise rejection operation is not degraded even by assumingthat noise amount does not depend on the line capacitance ratio Kc andis nearly constant when the noise component is removed by an operationalprocess using the line capacitance ratio Kc.

Although the operation method is not shown in detail, in a case wherethe noise source, of which the noise amount is associated with the linecapacitance ratio Kc, such as the incoming noise, is not negligible, itis possible to perform a noise rejection operation in which the noiseamount is not constant as well.

[Noise Rejection Operation]

Next, by focusing on a case where the signal component of the detectionsignal is different depending on the length of the sensor line, a noiserejection operation using the line capacitance ratio Kc obtained at thattime will be described.

FIG. 6A illustrates waveforms of a long sensor output and a short sensoroutput.

In FIG. 6A, the waveform diagram denoted by “Long Sensor(L)” representsthe output waveform of the long sensor line LSLi. In addition, thewaveform diagram denoted by “Short Sensor(S)” represents the outputwaveform of the short sensor line SSLi. In these output waveforms, theabscissa denotes changes of time t [μs], and the ordinate denotes anelectric potential fluctuation in the sensor line output with respect toa reference electric potential (for example, 0 m). In the abscissa, thetime is ranged from 0 to 16.67 [msec]. While the sensor line output alsofluctuates in an AC manner as a result of driving the driving electrodewith an AC voltage, a period of the electric potential fluctuation issignificantly small with respect to the abscissa of FIG. 6A, and thus, amountain of the AC waveform is represented as a line.

The area denoted by a border in FIG. 6A represents the area seen from adetection surface corresponding to the driving electrode DE activated byor connected to the AC signaling source AS in FIG. 4A or 5A.

FIG. 6B schematically illustrates a long sensor line outputcorresponding to the waveform diagram “Long Sensor(L)”. FIG. 6Cschematically illustrates a short sensor line output corresponding tothe waveform diagram “Short Sensor(S)”.

Here, the width of the border in the y-direction is set to be largerthan the movement pitch. This may be achieved by increasing the divisionnumber of the driving electrode DE shown in FIG. 5A but setting thenumber of the driving electrodes DE driven by the AC signaling source ASin a single time to a plural number. That is, the number of the drivingelectrodes DE driven in a single time is set to, for example, a few orseveral tens, and the pitch of shift during the scanning is set to, forexample, the number corresponding to a single driving electrode. Inaddition, while such a method of scanning using plural drivingelectrodes with a narrow pitch is dispensible in the present embodiment,such a method is employed in FIGS. 6A to 6C.

The numerals “0” and “800” shown in FIGS. 6B and 6C represent shiftpitch numbers in the y-direction. “0 to 400” corresponds to an area A,and “400 to 800” corresponds to an area B with respect to the center“400” thereof.

The border moves from the state shown in FIG. 6A along the arrowdirection.

In the scanning of the area A where only the long sensor line LSLiintersects with the border, the detection signal Vdet having thewaveform shown as “Long Sensor(L)” is output from the long sensor lineLSLi. In the scanning of the area A, the long sensor line output isobtained by defining that one time of the signal component S and onetime of the noise component are overlapped as shown in FIG. 6B. In thiscase, since the short sensor line output does not yet intersect with theborder as shown in FIG. 6C, only the noise component is output.

Here, as described in the [Noise Component] section, since it can beassumed that the noise component does not depend on the line capacitanceratio Kc and is constant, the noise component of the short sensor lineoutput is also represented as one time (=N).

In FIG. 6C, there are illustrated an operational formula (in the case ofKc=2) for obtaining the signal component S and a general formula usingthe line capacitance ratio Kc. As such, it is possible to obtain thesignal component S with the noise component being removed through anoperation by using the line capacitance ratio Kc from the outputs fromtwo sensor lines having a different length.

FIG. 7B illustrates a table representing the operation result from thedetection signal obtained during the scanning of three positions basedon the operational formula of FIG. 6C. FIG. 7A illustrates arelationship between the positions <1> to <3> and the sensor line.

In the operational circuit, the detection signal is sequentially inputin the order of the position <1> where the border is positioned in thearea B, the position <2> where the border width center is positioned inthe boundary between the areas A and B, and the position <3> where theborder is positioned in the area A. The operational circuit obtains thesignal component S by inputting the output of the long sensor line LSLiand the output of the short sensor line SSLi and performing an operationusing the difference (Delta) thereof and the line capacitance ratio Kc.

As shown in FIG. 7B, the operational circuit obtains only the difference(Delta) in the detection time range corresponding to the position <3>and performs an operation using the operational formula “(Delta)/(Kc−1)”based on the difference (Delta) and the line capacitance ratio Kc in thedetection time range corresponding to the position <1>. In addition, inthe detection time range corresponding to the position <2>, since thedifference (Delta) becomes zero in the case of, for example, Kc=2, andthe operation may not be possible, the operation is not performed in theintermediate detection time range.

In addition, a clock signal synchronized with the detection scanning,i.e., the shift operation of the border of FIG. 6A is input, and thedetection time ranges are determined based on the clock signal.

Alternatively, since the difference (Delta) directly becomes the signalcomponent S if Kc=2, the operational circuit may obtain the signalcomponent S by sampling the detection signal Vdet at the detectiontiming corresponding to the position <1> or <3>.

In addition, if the line capacitance ratio Kc is equal to or larger than3, the operational circuit may obtain the signal component S by samplingthe detection signal Vdet at the detection timing corresponding to theposition <3>. Meanwhile, in the case of the detection timingcorresponding to the position <1>, a general formula of the difference(Delta) becomes “(Kc−1)(Delta)”. Therefore, the operational circuit canobtain the signal component S by computing “(Delta)/(Kc−1)”.

The output from the operational circuit obtained as described above isprovided to a process of determining presence/absence of the detectiontarget object or a position thereof using a circuit (not shown)(including either an internal circuit or an external circuit of thecorresponding position detection device).

In addition, in the operation for two sensor lines having the samelength and a different width, in the case of the capacitance formula,the signal component of the detection signal is sometimes equal evenwhen the width is different as described in the first modification, andthe noise component is also sometimes equal as described in the [NoiseComponent] section. In that case, even when the widths are different,the ratio between the signal component and the noise component does notchange. Therefore, the operation using the line capacitance ratio Kc asin the aforementioned case where the lengths are different may not bepossible.

However, in a case other than the capacitance formula and also in thecapacitance formula, the noise component may change depending on theline capacitance ratio Kc, for example, as in the incoming noise. Inthis case, although detailed descriptions are omitted, it is possible toobtain the signal component S using the difference of the ratio betweenthe signal component and the noise component, similar to the case wherethe lengths are different.

[Configuration Examples of AC Signaling Source and Operational Circuit]

FIG. 8B is a circuit diagram illustrating configuration examples of theoperational circuit 8A and the AC signaling source AS of the touchdetection unit 8. FIG. 8A illustrates a driving position of the drivingelectrode.

In FIG. 8A, the hatched driving electrode DE1 is connected to andactivated by the AC signaling source AS, and other unselected drivingelectrodes DE2 to DEm are maintained in a ground electric potential GND.The state that the driving electrode is selected and activated isreferred to as an ON state, and the unselected state is referred to asan OFF state. FIG. 8B illustrates a circuit diagram of a singleoperational circuit 8A and an AC signaling source AS of the touchdetection unit 8 connected to any long sensor line LSLi (i=1 to n)intersecting with such a driving electrode group. The operationalcircuit 8A is a circuit for performing a predetermined operation betweenthe LSL output and the SSL output by also inputting the short sensorline SSLi (1=1 to n) neighboring to the long sensor line LSLi.

The (electrostatic) capacitance elements C1_1 to C1_m are formed in eachintersection between the long sensor line LSLi and the driving electrodeDej (j=1 to m).

The AC signaling source AS shown in FIG. 8B includes a control unit 91,two switches SW(+) and SW(−), a latch circuit 92, a buffer circuit(waveform shaping unit) 93, and an output switch SW. The control unit 91is a circuit for controlling the output switch SW and two switches SW(+)and SW(−) switching between the positive voltage V(+) and the negativevoltage V(−). The control circuit 91 may not be provided in the ACsignaling source AS but be substituted with an external CPU.

The switch SW(+) is connected between the positive voltage V(+) and thelatch circuit 92, and the switch SW(−) is connected between the negativevoltage V(−) and the input of the latch circuit 92. The output of thelatch circuit 92 is connected to the ON-side node of the output switchSW through the buffer circuit 93. The buffer circuit 93 is a circuit forcompensating for the input electric potential and outputting it to thepositive voltage V(+) and the negative voltage V(−). Here, the outputswitch SW is controlled by the control unit 91 so as to control whetherthe corresponding AC signaling source AS is turned on (selected oractivated) or connected to the ground (inactivated). Since the controlunit 91 is synchronized with the control of other AC signaling sourcesAS, the function of the control unit 91 is typically performed bysequentially transmitting a signal for shifting and selecting a group ofthe AC signaling sources AS to be activated to the shift register or thelike.

The operational circuit 8A is connected to the long sensor line LSLiwhere the (electrostatic) capacitance elements C1_1 to C1_m areconnected. While the operational circuit 8A is connected to the shortsensor line SSLi, the number the (electrostatic) capacitance elementsconnected to the short sensor line SSLi is a half of that of the longsensor lines LSLi.

The operational circuit 8A shown in FIG. 8 includes a differentialoperation unit (e.g., OP-Amp) 80, two coefficient multipliers (e.g.,OP-Amp circuit) 81, a rectifier circuit 82, and an output circuit 83.

As shown in FIG. 8B, the coefficient multiplier 81 may include an OP-Ampcircuit 84, resistors R1 and R2, and a capacitance C3. The coefficientmultiplier 81 functions as a multiplier for multiplying the input LSLoutput <L> or the SSL output <S> by a predetermined coefficient such asthe coefficient of FIG. 7B ((line capacitance ratio Kc=1/3 or 2/3). Thecoefficient multiplier 81 also has a function of rejectinghigh-frequency noise due to the capacitance C3 in addition to theresistors.

The coefficient multiplied by the coefficient multiplier 81 with aninput may be represented as (l+r2/r1) (where, r1 denotes a value of theresistor R1, and r2 denotes a value of the resistor R2). As thecoefficient multiplier 81 receives the LSL output <L>, the values of theresistors R1 and R2 are determined to satisfy (1+r2/r1)=⅓. As thecoefficient multiplier 81 receives the SSL output <S>, the values of theresistors R1 and R2 are determined to satisfy (1+r2/r1)=⅔.

In FIG. 8B, the long sensor line LSLi is connected to the non-invertedinput “+” of the IP-Amp 84, from which the detection signal Vdet (LSLoutput <L>) is input. The long sensor line LSLi is connected to a groundelectric potential through a reset switch RSW for electrically resettingthe DC level of the electric potential thereof. The resistor R2 and thecapacitance C3 are connected in parallel between the output of theOP-Amp 84 and the inverted input “−”, and the resistor R1 is connectedbetween the inverted input “−” of the OP-Amp 84 and the ground electricpotential.

This configuration is similarly applied to other coefficient multipliers81 connected to the short sensor line SSLi.

The differential operation unit 80 is, for example, an OP-Amp, of whichthe non-inverted input “+” is connected to the output of the coefficientmultiplier 81 that multiplies the coefficient by the output of the longsensor line LSLi. The inverted input “−” of the OP-Amp as thedifferential operation unit 80 is connected to the output of anothercoefficient multiplier 81 that multiplies the coefficient by the outputof the short sensor line SSLi.

The differential operation unit 80 extracts the SSL output <S> after thecoefficient multiplication from the LSL output <L> after the coefficientmultiplication and obtains a difference therebetween (or a difference ofabsolute values). Therefore, a difference signal representing thedifference (Delta)(=S) of FIG. 7B is output from the differentialoperation unit 80. Since this difference signal is an AC signal, it isconverted into a DC signal by the subsequent rectifier circuit 82 andcompared with a predetermined threshold value Vt in the output circuit83. In addition, when the operation “(Delta)/(Kc−1)” of FIG. 7B isperformed, a divider circuit is further provided so that the divisionresult thereof is compared with the threshold value Vt.

However, the rectifier circuit 82 and the output circuit 83 aredispensable. Therefore, for example, when the operation “(Delta)/(Kc−1)”is not performed, the difference signal output from the differentialoperation unit 80 may correspond to the detection signal of theembodiment of the present invention. Alternatively, a digital signalhaving a different logic depending on presence/absence of the detectiontarget object from the output circuit 83 may correspond to the detectionsignal of the embodiment of the present invention. In a case where theoperation “(Delta)/(Kc−1)” is performed, the signal output from thedivider circuit corresponds to the detection signal of the embodiment ofthe present invention. Anyway, the touch detection unit 8 can generatethe detection signal from the sensor line output.

The rectifier circuit 82 shown in the drawing includes a diode D1 forperforming the half-wave rectification, a charging capacitor C4, and adischarging resistor R0. The anode of the diode D1 is connected to theoutput of the coefficient multiplier 81, and the charging capacitor C4and the discharging resistor R0 are connected between the cathode of thediode D1 and the ground potential. The charging capacitor C4 and thedischarging resistor R0 constitute a smoothing circuit. The electricpotential of the cathode of the diode D1 (the output of the rectifiercircuit 82) is read as a digital value through the output circuit 83.

The output circuit 83 in the illustrated example includes only thecomparator 85 for comparing a voltage thereof with the threshold value.The output circuit 83 also has a function of the AD converter. The ADconverter may have any type such as a resistor ladder type or acapacitance dividing type. The output circuit 83 compares the inputanalog signal with the threshold value Vt (refer to FIG. 3A) using thecomparator 85. The comparator 85 may be implemented as a function of thecontrol circuit (not shown) such as a CPU. The comparison result is usedin various applications as a signal representing whether or not touchhas been performed, for example, whether or not the button manipulationhas been input.

In addition, the threshold value Vt as a reference voltage of thecomparator 85 may be substituted with a control unit such as a CPU, andthe electric potential of the detection signal Vdet can be determined asa result.

While a configuration example of the operational circuit 8A forcomputing the output of two sensor lines having a different length hasbeen described above, the configuration of the operational circuit 8Amay be determined suitable for the first to third modificationsdescribed above.

According to the first embodiment, two sensor lines having differentline parameters such as a length are arranged, the signal componentrepresenting the position of the detection target object and the noisecomponent are superimposed on the output of one of the sensor lines(e.g., a long sensor line). In addition, the output of the other one(e.g., a short sensor line) has a time period where only the noisecomponent is superimposed. The signal component has a valuecorresponding to the line capacitance ratio Kc of the sensor line, andnoise component has a constant value regardless of the line capacitanceratio Kc. Therefore, the touch detection device according to the firstembodiment can generally remove the noise component by performing anoperation process using the line capacitance ratio Kc for the two sensorline outputs.

5. Second Embodiment

According to the second embodiment, the outputs of three sensor lineshaving different line capacitances are used in the noise rejectionoperation process. The second embodiment is similar to the firstembodiment except for this fact. FIGS. 1A to 3C and 5A to 5C can bedirectly applied to the second embodiment. Configurations of FIG. 4 canbe applied to the second embodiment except for a pattern shape or anarrangement of the sensor lines.

FIGS. 9A to 9C are schematic diagrams illustrating a detection signalVdet similar to that of FIG. 6A to 6C of the first embodiment. FIGS. 10Aand 10B are a top plan view illustrating a border position similar toFIGS. 7A and 7B of the first embodiment and a table showing theoperation result (including an intermediate course)

According to the second embodiment, as shown in FIG. 10A, a long sensorline LSL, a middle sensor line MSL having a length corresponding to ⅔that of the long sensor line, and a short sensor line SSL having alength corresponding to ⅓ that of the long sensor line neighbors. Bysetting these three sensor lines to a single group, the operationalcircuit performs the operation using the line capacitance ratio Kcbetween the sensor line outputs.

In FIGS. 9A to 9C, the noise component N is represented as a constantvalue “3N” regardless of the length of the sensor line, and the signalcomponent is represented as a natural-numbered multiple (e.g., S, 2S,and 3S) of the smallest signal component S.

The noise component 3N is overlapped with the signal component S in theoutput of the long sensor line LSL of FIG. 9A. The noise component 2N isoverlapped with the signal component 2S in the output <M> of the middlesensor line MSL (hereinafter, referred to as an MSL output) of FIG. 9B.The noise component N is overlapped with the signal component 3S in theoutput of the short sensor line SSL (SSL output <S>) of FIG. 9C.

The operation results (including the intermediate result) using thethree sensor line outputs, i.e., the LSL output <L>, the MSL output <M>,and the SSL output <S> are shown in the table of FIG. 10B.

As shown in FIGS. 10A and 10B, in the position <1>, the operationalcircuit inputs “S+3N” as the LSL output <L>. In addition, theoperational circuit inputs 3N as the MSL output <M> and the SSL output<S>. In the difference operation, a difference Δ(L−M) between the LSLoutput <L> and the MSL output <M> or a difference Δ(L−S) between the LSLoutput <L> and the SSL output <S> can be obtained. In this case, adifference Δ(M−S) between the MSL output <M> and the SSL output <S>becomes zero.

Similarly, the difference operation is performed for other positions <2>to <5>, and the results are summarized in the table of FIG. 10B. Here,in the positions <2> and <4>, the MSL output <M> and the SLS output <S>are outputs in the area where the effective border width varies.

From the operational results above, it is possible to obtain the signalcomponent S that can be used in the area enveloped by a thick line inthe final operation output shown in the sections Δ(L−M), Δ(L−S), andΔ(M−S) of FIG. 10B. However, since there is an area having a negativevalue, an absolute difference operation is used when that area is used.

The detailed operation method described above is just exemplary, and thepresent invention is not limited thereto. The essence of the operationmethod is that the noise rejection can be readily performed using theline capacitance ratio Kc because the detection signal Vdet has thesignal component and the noise component in proportion to the linecapacitance ratio Kc.

According to the second embodiment, three sensor lines having adifferent line parameter such as a length are arranged, and the noisecomponent and the signal component representing the position of thedetection target object are superimposed on the outputs of all thesensor lines. However, the outputs of the sensor line of a middle lengthand a shortest sensor line have a time period in which only the noisecomponent are superimposed. The signal component has a valuecorresponding to the line capacitance ratio Kc of the sensor line, andthe noise component has a generally constant value. Therefore, the touchdetection device according to the second embodiment can generally removethe noise component by performing the operation process using the linecapacitance ratio Kc for these three sensor line outputs.

Although the operation process becomes more complicated in the case ofthree line sensors than the two sensor lines, it is possible tocalculate the signal component S by the operation even in a time rangein which the border (the range of the driving electrodes activatedduring scanning) is overlapped in the leading end of the sensor line.Therefore, according to the second embodiment, it is advantageous inthat the presence/absence or the position of the detection target objectcan be determined in a seamless manner in the y-direction.

In practice, since the coefficient is determined considering a parasiticcapacitance between the wiring line and the TFT element, between thewiring lines, or the like, it may not be an integer multiple. However,by setting the parameter (in this case, the length of the sensor lineSL) using the line capacitance ratio Kc and performing the operationusing the parameter, even when the noise may not be perfectly removed,it is possible to obtain a sufficient noise suppression effect inpractice. This is the same in the first embodiment of FIGS. 7A and 7B(because the coefficient is not an integer multiple in a strict sense,and even in this case, a sufficient noise suppression effect can beobtained).

6. Third Embodiment

The third embodiment relates to a display device according to thepresent invention. The function of the touch sensor of this displaydevice is similar to that of the first or second embodiment.

The display device exemplified in this embodiment is a liquid crystaldisplay device, particularly, for removing the noise superimposed by theVcom-driving.

According to the embodiment of the present invention, the Vcom-drivingis dispensable. However, in the following description, it is exemplifiedthat a liquid crystal display device performs the Vcom-driving andsimultaneously performs the display scanning (write scanning) and thesensor driving scanning by using the common electrode (oppositeelectrode) for the sensor driving as well as the display drivingthereof. While this liquid crystal display device is advantageous inthat the entire device can be thin, it is disadvantageous in that thenoise source is in proximity of the sensor line within a shorterdistance. Therefore, the embodiment of the present invention can beeffectively applied.

In addition, the “opposite electrode” of the embodiment of the presentinvention refers to an electrode which takes a function of the drivingelectrode for detecting touch, similar to the first embodiment, as wellas a function of the common electrode for the display driving of thesecond embodiment. Hereinafter, in order to maintain consistency withthe first embodiment, the term “driving electrode DE” of the firstembodiment will continuously used.

While the sensor detection accuracy is proportional to the number ofsensor lines (in the present embodiment, referred to as a “sensingelectrode”), the number of sensor lines becomes enormously large if thesensor lines are arranged in a matrix shape along the x-direction andthe y-direction. In order to reduce the number of sensor lines, adriving method is desirable in which one of a plurality of drivingelectrodes is driven with an AC voltage, and such a target of the ACdriving is shifted within the arrangement of a plurality of drivingelectrodes lined up with a constant pitch and a predetermined interval.This driving method itself is employed in the first embodiment.Therefore, it is possible to obtain the sensor output using only thesensor lines extending in the y-direction. Hereinafter, the direction ofshifting the operation target of these driving electrodes is referred toas a scanning direction.

In such a technique for scanning the driving target in a scanningdirection (the y-direction), if the voltage variation on the sensor lineis observed along the scanning, it is possible to detect touch orproximity on the touch panel surface of the detection target object fromthe position of the scanning having the electric potential variation.

Application of the embodiment of the present invention is not limited tothe driving method in which the driving electrodes are divided in they-direction and driven by a predetermined number to shift the drivingtarget. However, since the miniaturization is desirable, the followingdescription will be made based on this driving method.

[Schematic Configuration of Display Device]

FIGS. 11A to 11C are top plan views particularly illustrating electrodesof the display device according to an embodiment of the presentinvention and a circuit arrangement for driving or detecting theelectrodes. FIG. 11D illustrates a schematic cross-sectional structureof the display device according to an embodiment of the presentinvention. FIG. 11D shows a cross-section corresponding to 6 pixels, forexample, in a row direction (pixel display line direction). FIGS. 13A to13C are equivalent circuit diagrams of pixels.

The display device shown in FIG. 11A to 11D is a liquid crystal displaydevice having a liquid crystal layer as the “display function layer.”

The liquid crystal display device has, as an electrode common to aplurality of pixels out of two facing pixels with the liquid crystallayer being interposed therebetween, an electrode (driving electrode)where the common driving signal Vcom for applying a reference voltage tothe signal voltage for the gray-scale display for each pixel is applied.

In FIG. 11D, in order to make it easy to see the cross-sectionalstructure, while the driving electrode, the pixel electrode, and thesensing electrode as main components of the embodiment of the presentinvention are hatched, other portions (such as a substrate, aninsulation film, and a functional film) are not hatched. The omission ofhatched lines will be similarly applied to other cross-sectional viewssubsequently described.

The pixels PIX shown of the liquid crystal display device 1 of FIG. 12is arranged in a matrix shape. As shown in FIG. 12, each pixel PIXincludes a thin film transistor TFT23 as a selection element of thepixel, an equivalent capacitance C6 of the liquid crystal layer 6, and aretentive capacitance Cx (also, referred to as an additionalcapacitance). The electrode arranged in one side of the equivalentcapacitance C6 representing the liquid crystal layer 6 is a pixelelectrode 22 divided for each pixel and arranged in a matrix shape, andthe electrode arranged in the other side is a driving electrode 43common to a plurality of pixels.

The pixel electrode 22 is connected to one of the source and the drainof the thin film transistor TFT23, and the image signal line SIG isconnected to the other one of the source and the drain of the thin filmtransistor TFT23. The image signal line SIG is connected to a verticaldriving circuit (not shown, refer to FIG. 13A to C of the embodimentsdescribed below) so that the image signal having a signal voltage issupplied from the vertical driving circuit to the image signal line SIG.

The driving electrode 43 is provided with the common driving signalVcom. The common driving signal Vcom is obtained by inverting betweenpositive and negative electric potentials for each horizontal cycle (1H)with respect to the center voltage.

The gate of the thin film transistor TFT23 is electrically shared amongall pixels PIX lined up in a row direction, i.e., in a horizontaldirection of the display screen so that the scanning line SCN is formedas a result. The scanning line SCN is supplied with a gate pulse outputfrom the vertical driving circuit (not shown) for turning on/off thegate of the thin film transistor TFT23. Therefore, the scanning line SCNis also referred to as a gate line.

As shown in FIG. 12, the retentive capacitance Cx is connected to theequivalent capacitance C6 in parallel. The retentive capacitance Cx isprovided to prevent a write electric potential from decreasing by theleak current from the thin film transistor TFT23 due to shortage of thestorage capacity in the equivalent capacitance C6. In addition, additionof the retentive capacitance Cx contributes to preventing flickers orimproving uniformity of the screen luminance as well.

From the viewpoint of the cross-sectional structure (FIG. 11D), theliquid crystal display device 1 having such pixels includes a panel(hereinafter, referred to as a driving panel 2) which has a thin filmtransistor TFT23 shown in FIG. 12 in the area not shown in the crosssection and is supplied with a driving signal (signal voltage) of thepixel, an opposite panel 4 arranged to face the driving panel 2, and aliquid crystal layer 6 arranged between the driving panel 2 and theopposite panel 4.

The driving panel 2 has a TFT panel 21 (of which a panel body unit ismade of glass) as a glass substrate having the thin film transistorTFT23 of FIG. 12 and a plurality of pixel electrodes 22 arranged on thisTFT panel 21 in a matrix shape.

A display driver (not shown) for driving each pixel electrode 22(including the vertical driving circuit, the horizontal driving circuit)is formed on the TFT panel 21. The thin film transistor TFT 23 of FIG.12 and wiring lines such as the image signal line SIG and the scanningline SCN are formed on the TFT panel 21. The touch detection unit 8(refer to FIGS. 4A, 4B, 8A, and 8B) of the first embodiment may beformed on the TFT panel 21.

The opposite panel 4 includes a glass substrate 41, a color filter 42formed on one surface of the glass substrate 41, and a driving electrode43 formed on the color filter 42 (the liquid crystal layer 6 side). Thecolor filter 42 is configured by periodically arranging three colorfilter layers having, for example red, green, and blue colors (R, G, andB), and each pixel PIX (pixel electrode 22) corresponds to one of thethree colors R, G, and B. While in some cases, a pixel corresponding toone color is called a subpixel, and three subpixels having three colorsR, G, and B are called a pixel, the subpixel is also called a pixel PIXherein.

The driving electrode 43 is also used as the driving electrode DE (referto the first and second embodiments) of the touch detection sensorincluded in a part of the touch sensor for performing the touchdetection operation. The opposite electrode 43 corresponds to thedriving electrode E1 of FIGS. 1A to 2B.

The driving electrode 43 is connected to the TFT panel 21 by the contactconductive pillar 7. The common driving signal Vcom having an AC pulsewaveform is applied from the TFT panel 21 to the driving electrode 43through the contact conductive pillar 7. The common driving signal Vcomcorresponds to the AC pulse signal Sg supplied from the driving signalsource S of FIGS. 1A to 2B.

The other surface (display surface side) of the glass substrate 41 isprovided with the sensor line SL, and the protection layer 45 is formedon the sensor line SL. The sensor line SL constitutes a part of thetouch sensor and corresponds to the detection electrode E2 in FIGS. 1Ato 2B. The glass substrate 41 may have a touch detection unit 8 forperforming the touch detection operation described below (refer to FIGS.8A and 8B).

The liquid crystal layer 6 as a display function layer modulates thelight passing through the thickness direction (a direction facing theelectrode) according to the state of the applied electric field. Theliquid crystal layer 6 may be formed using various modes of liquidcrystal materials such as TN (twisted nematic), VA (vertical alignment),and ECB (electrically controlled birefringence).

The alignment film is provided between the liquid crystal layer 6 andthe driving panel 2 and between the liquid crystal layer 6 and theopposite panel 4. A polarization plate is provided in the anti-displaysurface side (i.e., back surface side) of the driving panel 2 and thedisplay surface side of the opposite panel 4. Such an optical functionlayer is omitted from FIG. 11 A to 11D.

[Configuration of Driving Electrode and Driving Scanning]

As shown in FIG. 11A, the driving electrode 43 is divided in a row orcolumn direction of the pixel arrangement, e.g., in a column directionin this example (the vertical direction of the drawing). This divisiondirection corresponds to a scanning direction of the pixel lines in thedisplay driving, i.e., a direction for sequentially activating thescanning lines SCN by the vertical driving circuit (not shown).

The driving electrode 43 is divided into a total of (k×m) drivingelectrodes. Therefore, driving electrodes 43_1, 43_2, . . . , 43_k, . .. , 43_km are arranged in a planar band-shaped pattern extending in arow direction and spaced from one another in parallel on thecorresponding surface.

A division arrangement pitch of the (k×m) driving electrodes 43_1 to43_km is set to a natural-numbered multiple of the (sub)pixel pitch orthe arrangement pitch of the pixel electrodes.

In addition, in FIGS. 11A to 11D, the driving electrodes DE are a set ofk driving electrodes 43 (k>2) and driven by an AC voltage in this unit.The unit of the AC driving is set to be larger than one pixel linebecause the detection sensitivity can be improved by increasing theelectrostatic capacitance of the touch sensor. Meanwhile, it is possibleto accommodate invisualization of shifting by shifting the drivingelectrodes DE by a natural-numbered multiple of pixel pitch unit.

Meanwhile, during the Vcom-driving in the unit of the driving electrodesDE in this manner, the shifting is performed by the scan driving unit 9as an AC driving scanning unit provided within the vertical drivingcircuit (the write driving scanning unit)(not shown). The operation ofthe scan driving unit 9 can be considered to be the same as “theoperation of scanning in a column direction while switching one by onethe driving electrodes selected by moving, in a column direction, the ACsignaling source AS which simultaneously drives the wiring lines of thek driving electrodes with an AC voltage Vcom (refer to FIGS. 1A and 1B,2A and 2B, and 8A and 8B).”

Meanwhile, similar to the first embodiment, the sensor lines SL areobtained by alternately arranging the n long sensor lines LSLi and nshort sensor lines SSLi. A total of 2n sensor lines SL are formed ofparallel stripe wiring lines extending in the y-direction. Out of the 2nsensor lines, the LSL output <L> is output from the long sensor lineLSLi, and the SSL output <S> is output from the short sensor line SSLi.These 2n sensor line outputs are input to the touch detection unit 8,for example, using an exemplary operational circuit 8A shown in FIG. 8Bas basic detection unit.

In addition, FIGS. 11A and 11B are diagrams separated to describe theelectrode pattern. However, in practice, as shown in FIG. 11C, thedriving electrodes 43_1 to 43_km and the sensor lines (the long sensorline LSLi and the short sensor line SSLi) are overlappingly arranged todetect the position within a 2-dimensional plane. In this configuration,the touch detection unit 8 can detect the position of the row directionbased on which operational circuit 8A generates the voltage variationand obtain the position information in a column direction based on thedetection timing. In other words, the Vcom-driving of the scan drivingunit 9 and the operation of the touch detection unit 8 are synchronizedwith, for example, a clock signal having a predetermined period. Throughsuch a synchronization operation, the touch detection unit 8 can detecta finger touch position center because it is possible to know whichdivided driving electrode is driven by the scan driving unit 9 when thetouch detection unit 8 obtains the voltage variation. Such a detectionoperation is controlled by a computer-based total control circuit (notshown) which totally controls the liquid crystal display device 1, forexample, a CPU, a microcomputer, or a control circuit for detectingtouch.

While the scan driving unit 9 as the “AC driving scanning unit” isformed on only the driving panel 2 side of FIG. 11D, the touch detectionunit 8 may be formed in the driving panel 2 side as well as the oppositepanel 4 side. Since the TFTs are integrated with a high density, it isdesirable that the touch detection unit 8 is also provided in thedriving panel 2 in order to reduce the manufacturing process number.However, since the sensor line SL exists in the opposite panel 4 side,and the sensor line SL is formed of a transparent electrode material,the wire resistance may increase. In that case, in order to avoiddifficulties such as a high resistance of the wiring lines, it ispreferable that the touch detection unit 8 is formed in the oppositepanel 4 side. However, if the process of forming the TFT is used in theopposite panel 4 only for the touch detection unit 8, itdisadvantageously demands high cost. The position for forming the touchdetection unit 8 may be determined by comprehensively considering theaforementioned advantages and disadvantages.

FIG. 13 illustrates such an AC driving operation and the shiftoperation.

In FIGS. 13A to 13C, a single driving electrode DE is constructed of 7hatched driving electrodes 43. Here, the driving electrode 43 isdifferent from the driving electrode DE in that k driving electrodes 43simultaneously driven are called driving electrodes DE.

FIGS. 13A to 13C illustrate a progress of the selection range when thedriving electrodes DE are shifted in the unit of a single pixel line,i.e., by a pitch of a single driving electrode 43 in a column direction.

In the time T1 of FIG. 13A, an initial single pixel line is notselected, but k driving electrodes corresponding to second to eightpixel lines are selected and simultaneously driven by the AC signalingsource AS with an AC voltage.

In the next cycle (time T2), the driving electrodes DE are shifted by asingle pixel line so that two driving electrodes corresponding to thefirst and second pixel line are not selected, 7 driving electrodessubsequent to the third driving electrode are selected, and others arenot selected.

Furthermore, in the next cycle (time T3), the driving electrodes DE areshifted by a single pixel line so that driving electrodes correspondingto the first to third lines are not selected, 7 driving electrodessubsequent to the fourth driving electrode are selected, and others arenot selected. Then, the shifting and the AC driving operations aresimilarly repeated.

Through such operations, the value of m in the equation of FIG. 5C isreduced by 1/7 of the practical dividing number so that the effectivevalue of the sensor voltage Vs increases accordingly. Meanwhile, asshown in FIGS. 13A to 13C, the unit that is newly included in andexcluded from the selection group (the driving electrode DE) is a singledriving electrode corresponding to a single pixel line. Therefore, theswitching frequency of the AC driving becomes equal to the inversionfrequency 1H of the common driving signal Vcom. This frequency is anextremely high frequency obtained by multiplying a commercial electricpower frequency, e.g., 60 [Hz] by the number of pixels in the columndirection. For example, the number of pixels in the column direction isset to 480, this frequency becomes 28.8 [kHz], and the frequency of thepulse waveform becomes 14.4 [kHz] which is a half thereof. Therefore, animage variation caused by the shifting of the AC driving has asufficient high frequency unrecognizable by a human eye. Consequently,it is possible to prevent both the S/N ratio reduction caused by thesensor voltage falling and the image quality degradation caused by theswitching of the electrode driving.

[Arrangement of Pixel Electrode and Image Signal Line]

FIG. 14 is an enlarged plan view illustrating a display unit in themiddle of a manufacturing process of forming the pixel electrode 22.

In the plan view of FIG. 14 in the middle of a process of forming thepixel electrode 22, a plurality of gate lines (scanning lines SCN, referto FIG. 12) arranged in a parallel stripe shape in a row direction(x-direction) intersect with a plurality of image signal lines SIGarranged in a parallel stripe shape in a column direction (y-direction.The rectangular area surrounded by two arbitrary scanning lines SCN andtwo arbitrary image signal lines SIG defines the (sub)pixel PIX. Thepixel electrode 22 is formed in the rectangular isolation patternslightly smaller than each pixel PIX. As such, a plurality of pixelelectrodes 22 are arranged in a matrix shape in a planar shape.

[Display Operation]

Next, operations of the display device having the aforementionedconfiguration will be described.

The display driver of the driving panel 2 (the horizontal drivingcircuit and the vertical driving circuit that are not shown)sequentially supplies line by line each electrode pattern of the drivingelectrodes 43 (driving electrodes 43_1 to 43_km) with the common drivingsignal Vcom. In this case, the method of selecting the driving electrodeand the shifting method are similar to those described above. The commondriving signal Vcom is also used to control the electric potential ofthe driving electrode of the image display. In addition, the displaydriver supplies the pixel electrode 22 with a signal voltage through theimage signal line SIG and also sequentially controls line by line theswitching of the TFT of each pixel electrode through the scanning lineSCN in synchronization therewith. As a result, in the liquid crystallayer 6, an electric field in a vertical direction (perpendicular to thepanel) determined by the common driving signal Vcom and each pixelsignal is applied to each pixel to modulate the liquid crystal state. Asa result, a display operation by a so-called inverted driving isperformed.

Meanwhile, in the opposite panel 4 side, the capacitance element C1 isformed in each of the intersections between the driving electrodes 43_1to 43_km and the long sensor line LSLi or the short sensor line SSLi.The common driving signal Vcom is sequentially applied to each electrodepattern of the driving electrode 43 in a time division manner. Then,each of the capacitance elements C1 corresponding to a single columnformed in intersections between the electrode patterns of the drivingelectrode 43 where the common driving signal Vcom is applied and theelectrode patterns of the sensor lines (LSLi and SSLi), ischarged/discharged. As a result, the output from the sensor line (LSLiand SSLi) has a magnitude corresponding to the capacity of thecapacitance element C1. In a state that a user's finger touches thesurface of the opposite panel 4, the magnitude of this sensor lineoutput becomes nearly constant (to a sensor voltage Vs). In addition tothe scanning of the common driving signal Vcom, the columns of thecapacitance elements C1 corresponding to the target of thecharge/discharge operations are sequentially shifted line by line.

Here, if a user's finger touches any place on the surface of theopposite panel 4, the capacitance element C2 caused by the finger isadded to the capacitance element C1 that has been originally formed inthe touched portion. As a result, a value (sensor voltage Vs) of thesensor output when that touched portion is scanned becomes smaller thanthose of other portions (becomes the sensor voltage Vf (<Vs)). The touchdetection unit 8 (refer to FIGS. 8A and 8B and 11A to 11D) performs theoperation process shown in FIG. 7B using each operational circuit 8A togenerate the detection signal Vdet. In addition, the detection signalVdet is compared with the threshold value Vt. If the detection signalVdet is equal to or smaller than the threshold value Vt, that portion isdetermined as the touched portion. This touched portion can be obtainedfrom the timing when the common driving signal Vcom is applied and thetiming when the detection signal Vdet equal to or smaller than thethreshold value Vt is detected.

As such, according to the third embodiment of the present invention, thecommon electrode (driving electrode 43) originally provided in theliquid crystal display device for driving the liquid crystal is alsoused as one of a touch sensor electrode pair including the drivingelectrode and the sensing electrode. The electrostatic capacitanceelement type touch sensor is constructed such that the common drivingsignal Vcom as the display driving signal is also used as the touchsensor driving signal. Therefore, an electrode to be newly provided toadd the touch sensor function is just the sensor line, and a unit forgenerating the touch sensor driving signal is not necessary to newlyprovided. Therefore, the configuration is simple.

In addition, a plurality of k driving electrodes 43 are simultaneouslydriven with an AC voltage, and by using these driving electrodes as asingle driving electrode DE, the driving electrode DE is shifted suchthat all of the driving electrodes 43 are selected by performing the ACdriving twice. For this reason, it is possible to prevent both reductionof the S/N ratio of the sensor detection voltage and image qualitydegradation. Furthermore, since the driving electrode and the drivingcircuit for the common driving signal Vcom can also be used as thedriving electrode and the driving circuit for the sensor, it is possibleto accordingly reduce arrangement space and power consumption.

In addition, in FIGS. 4A, 4B and 14, while the sensor line SL is shownas a line having a predetermined width and two types of lengths, themodifications of the first and second embodiments can also be applied tothe third embodiment.

Hereinafter, some modifications of the third embodiment will bedescribed.

7. Fourth Modification

The structure and the driving method of the display device describedabove in conjunction with the third embodiment is advantageous in thatthe thickness of the (liquid crystal) display device obtained byintegrating the touch panel can be thinned.

However, even in the case where the touch panel is integrated into thedisplay panel, the driving electrode of the touch sensor may be providedin a different layer from the driving (common) electrode for the (liquidcrystal) display. In this case, the driving electrodes of the touchsensor may be arranged as a single electrode facing a plurality of pixelelectrodes without separation. However, the sensor lines are arranged ina matrix shape where the first sensor line group extending in they-direction and the second sensor line group extending in thex-direction intersect with each other. A single electrode used only forthe driving electrode of the touch sensor is arranged to be capacitivelycoupled to both the first sensor line group and the second sensor linegroup with a predetermined strength. The embodiment of the presentinvention is applied to both the first and second sensor line groups. Inother words, the second sensor line group of the x-direction as well asthe first sensor line group of the aforementioned y-direction is made tohave a plurality of line capacitances by changing, for example, a typesuch as a length. In the second sensor line group of the x-direction aswell as the first sensor line group, a process of removing noise by theoperation using the line capacitance ratio is performed for a pluralityof sensor line outputs having a different line capacitance. As a result,in the display device having the touch detection function and the sensorlines arranged in a matrix shape, it is possible to effectively removenoise and improve sensor detection accuracy.

In addition, the matrix arrangement of the sensor lines may beapplicable to the touch detection device described in conjunction withthe first and second embodiments.

8. Fifth to Seventh Modifications

The liquid crystal layer 6 is used to modulate the light passingtherethrough in response to the electric field state, and, for example,liquid crystals of a horizontal electric field mode such as a FFS(Fringe-field switching) mode or an IPS (in-plane switching) mode arepreferably used.

FIGS. 15 to 17 illustrate a constructional example of a horizontalelectric field mode liquid crystal display device.

In the structure shown in FIG. 11B, the pixel electrode 22 and thedriving electrode 43 face to each other with the liquid crystal layer 6being interposed therebetween. An electric field in a vertical directionis applied to the liquid crystal layer 6 in response to the voltageapplied between both the electrodes.

In the horizontal electric field mode, the pixel electrode 22 and thedriving electrode 43 are arranged in the driving panel 2 side.

In the structure of the fifth modification shown in FIG. 15, the drivingelectrode 43 is disposed in the surface of the front side of the TFTpanel 21 (the display surface side), and the driving electrode 43 andthe pixel electrode 22 neighbor to each other by interposing theinsulation layer 24. The driving electrode 43 is arranged in a lineshape extending in a display line direction (x-direction), and the pixelelectrode 22 is separated for each pixel in that direction.

The TFT panel 21 is bonded to the glass substrate 41 such that the pixelelectrode 22 side is adjacent to the liquid crystal layer 6. The liquidcrystal layer 6 is structurally maintained by a spacer (not shown).

The reference numeral “49” denotes a base material disposed in thedisplay surface side such as glass or a transparent film. One surface ofthe base material 49 is provided with the sensor line SL. The sensorline SL maintained in the base material 49 is fixed to the surface ofthe anti-liquid crystal side of the glass substrate 41 by the bondinglayer 48.

Meanwhile, a first polarization plate 61 is attached to the back surfaceof the TFT panel 21, and a second polarization plate 62 having adifferent polarization direction is attached to the display surface sideof the base material 49.

A protection layer (not shown) is formed in the display surface side ofthe second polarization plate 62.

In the structure of the sixth modification shown in FIG. 16, the colorfilter 42 is previously formed in the liquid crystal side of the glasssubstrate 41. The color filter 42 has a different color area regularlyarranged for each (sub)pixel.

In the structure of the seventh modification shown in FIG. 17, the stackstructure of the display surface side is different from that of FIG. 16.

In the structure of FIG. 16, the sensor line SL is previously formed onthe base material 49 and attached, for example, as a roll shape member.However, in FIG. 17, the sensor line SL is formed on the display surfaceside of the glass surface 41, and the second polarization plate 62 isattached thereon.

Next, modifications (eighth to eleventh modifications) common to theaforementioned first to third embodiments and first to seventhmodifications will be described.

9. Eighth Modification

The length of the short sensor line SSLi of the eighth modificationshown in FIG. 18 is extremely short. This is intended to dedicatedly usethe extremely short sensor line SSLi for detecting the noise component Nthat is not overlapped with the signal component S by arranging theshort sensor line SSLi in an outer side from the detection surface.

This modification is particularly effective in the second embodiment inwhich sensor lines having three lengths are provided.

In the table of FIG. 10B, it is assumed that this extremely short sensorline ESSL exists, for example, only in the position <5>. Then, a valueof the SSL output <S> corresponding to the extremely short sensor lineoutput, i.e., “3S+3N” is represented as just “3N”. Meanwhile, the LSLoutput <L> becomes “S+3N.” Therefore, it is possible to calculate thesignal component S just by subtracting the extremely short sensor lineoutput from the LSL output <L> so that the used portions increase.

10. Ninth Modification

In the ninth modification shown in FIG. 19, the arrangement order of thesensor lines that were arranged in the order of MSL, LSL, and SSL inFIG. 10A is arbitrarily set. For example, in FIG. 19, three sensor linesare arranged in the order of SSL, LSL, and MSL. As such, the arrangementorder of the sensor lines is arbitrarily set.

The sensor lines may not be arranged regularly as in FIGS. 18 and 19,but the sensor lines having different lengths within a pair of two or agroup of three may be arranged apart if they correspond to theoperational circuit 8A side. However, since the configuration of theoperational circuit 8A can be perfectly the same, the sensor lines arepreferably arranged on a regular basis. Here, the “different types of Msensor lines are periodically repeatedly arranged” in the regulararrangement.

11. Tenth Modification

In the tenth modification, a single operational circuit 8A and anotherneighboring operational circuit 8A share a single sensor line.

For example, in FIG. 20, a single extremely short sensor line ESSL isshared by two input operational circuits 8A. In addition, in FIG. 21,the MSL and the SSL are alternately shared by neighboring operationalcircuits 8A. In addition, if many types of the lengths are used, twosensor lines may be shared. Further, a selector (not shown) forswitching the shared sensor line for a plurality of operational circuitmay be provided.

Such a sharing structure includes a structure in which “two operationalcircuits 8A are connected to the same sensor line, and different typesof sensor lines are symmetrically arranged with respect to the commonsensor line in the two operational circuits.”

12. Eleventh Modification

The extremely short sensor line ESSL may be arranged in an outer sidefrom the detection surface or the effective area of the display surface,and the surface making contact with the detection target object may becovered with a shield layer 70 as shown in FIG. 22. Such a configurationis to consider a case where the incoming electromagnetic noise degradesthe noise rejection accuracy such as a case where a relationship betweenthe incoming electromagnetic noise and the line capacitance ratio Kc islittle. As a result, the effect of the incoming electromagnetic noise isnot removed by the operation circuit 8A. However, if the operationalcircuit 8A extracts the incoming electromagnetic noise which varies fromtime to time from the sensor line output, an error increases sometimes.If the shield layer 70 is provided, the incoming electromagnetic noisecomponent is not included in the noise component N. Therefore, it ispossible to suppress unevenness of the detection error.

In addition, as shown in FIG. 22, it is possible to improve thecomputation accuracy by shielding the operational circuit 8A.

13. Noise Source of Display Device and Noise Suppression Effect

Next, similar to the third embodiment, a noise source having asignificant effect when the touch sensor function is mounted on thedisplay device will be described.

While various noise sources of the touch sensor have been alreadydescribed in conjunction with the first embodiment, the wiring linehaving a strong capacitive coupling to the sensor line is the wiringline having a large electric potential variation and arranged inparallel with the sensor line. Particularly, as the display devices aremade thinner, they tend to have a reduced interval between this wiringline and the sensor line. Such a wiring line may include an image signalline SIG. As shown in FIG. 14, the image signal line SIG is arranged inthe y-direction, the same direction as that of the sensor line, andprovides an AC signal, of which a reference electric potential of theimage signal fluctuates, having an opposite phase to the electricpotential Vcom with a period of 1H (1 horizontal display cycle)corresponding to the voltage Vcom of the driving electrode 43.

FIG. 23A illustrates an electric potential waveform of the long sensorline LSLi in a case where the entire display is set to a white displayand in a case where the entire display is set to a black display forcomparison. FIG. 23B illustrates an electric potential waveform of theshort sensor line SSLi where only the noise component N is depicted forcomparison between the white display and the black display.

As shown in FIG. 23A, the sensor line output significantly changes inresponse to the display of the display device. This is because the noisecomponent N shown in FIG. 23B periodically changes with an oppositephase in every cycle 1H. The following two reasons are contemplated as areason of generating the noise component N.

As a first reason, the phase of the electric potential fluctuation ofthe driving electrode DE driven by the voltage Vcom is inverted in everycycle 1H. As a second reason, the reference level of the image signal atthe image signal line SIG is also inverted in every cycle 1H inassociation with the Vcom-driving.

However, since the former is not different between the white display andthe black display, the latter is the reason. That is, since the phase ofthe reference electric potential of the image signal is inverted by 180°against the driving electric potential Vcom, the reference electricpotential fluctuation of the image signal allows the voltage differencein the sensor line to be reduced in the white display and enlarged inthe black display. Referring to the waveform LSL of FIG. 23A and thewaveform SSL of FIG. 23B, the period of the black display changes in thesame phase, but the period of the white display changes in the oppositephase. This fact supports the aforementioned reason.

FIGS. 24B1 to 2483 illustrate the effect of the embodiment of thepresent invention. FIGS. 24A1 to 24A3 associated with the white displayand FIGS. 24B1 to 24B3 associated with the black display are waveformdiagrams by shifting the phase of the one side by 180° against the phaseof the other side.

In addition, FIGS. 24A1 and 24B1 are waveform diagrams at the longsensor line LSLi where the noise component N and the signal component Sare overlapped. FIGS. 24A2 and 24B2 are waveform diagrams illustratingonly the noise component N. FIGS. 24A3 and 24B3 are waveform diagramsafter the noise rejection.

For example, the waveform of the LSL output <L>(=S+3N) when the border(driving electrode DE) exists in the position <1> of the table of FIG.10B corresponds to FIGS. 24A1 and 24B1. In this case, the numeral “3N”in the box of the short sensor associated with the position <1> in FIG.10B corresponds to FIGS. 24A2 and 24B2. In addition, the waveform ofFIG. 24A3 is obtained by subtracting the waveform of FIG. 24A2 from thewaveform of FIG. 24A1. Similarly, the waveform of FIG. 24B3 is obtainedby subtracting the waveform of FIG. 24B2 from the waveform of FIG. 24B1.

It is recognized from FIGS. 24A3 and 24B3 that the electric potentialdifference (noise) is suppressed to nearly zero, while it reaches 0.8 mat maximum in FIG. 24A1 of the white display and FIG. 24B1 of the blackdisplay.

Based on the descriptions above, it was clarified that the displaydevice according to the embodiment of the present invention isparticularly effective to noise suppression when the electric potentialfluctuation in the image signal line functions as the noise source.

14. Other Effects

When such a noise source is contemplated, it is preferable that two orthree sensor lines are arranged with the same distance from the wiringline functioning as the noise source. For example, it is preferable thatthe sensor lines are arranged as close as possible from each other. Forthis reason, it is preferable that the sensor line has a narrow width.In other words, when the control is performed by the width, it isdifficult to arrange the sensor lines with the same distance from thenoise source although the operation advantageously becomes simple. Onthe contrary, when the control is performed by the length, it is easy toarrange the sensor lines with the same distance from the noise sourcealthough the operation may become more complicated in comparison withthe width control case.

Consequently, referring to FIG. 18 or FIG. 19, it is appreciated that adistance between the sensor lines connected to the same operationalcircuit 8A is set to be as small as possible.

In addition, in the configuration where a sensor line is shared by twoneighboring operational circuits 8A as shown in FIGS. 20 and 21, it ispossible to increase the sensor line density without degrading thedetection sensitivity in the x-direction. In other words, if a margin isprovided to the sensor line density in the x-direction under theconstriction that the combined sensor lines are arranged with the samedistance from the noise source, it is possible to improve thesensitivity by increasing the number of sensor lines. Therefore, it ispossible to detect touch with improved accuracy and sensitivity.

Since the shield layer 70 is provided as shown in FIG. 22, it ispossible to achieve a more accurate noise rejection process by excludingincoming electromagnetic waves functioning as a noise source usuallyfluctuating at random. In addition, errors can be effectively preventedby shielding the operational circuit 8A as well using the shield layer70.

It is preferable that the detection sensitivity in the y-direction canbe improved by performing the border scanning as described in the thirdembodiment, i.e., simultaneously driving a plurality of k drivingelectrodes 43 (the border) and shifting the border by a minimum pitchcorresponding to a single pixel pitch. Through the border scanning, itis possible to obtain an additional effect such as invisualization ofthe driving electrodes. From the viewpoint of the invisualization, forexample, invisualization may be improved by arranging dummy sensor linesin a portion where no sensor line exists among the middle sensor linesMSL or the short sensor lines SSL so that the long sensor line LSL isconstantly viewed from the external side.

In addition, since the reset switch RSW is provided for each operationalcircuit 8A, the operation can be made by excluding the remainingelectric charges. Therefore, it is possible to improve accuracy of theoperation. In addition, it is possible to obtain more accurate operationresults by nearly simultaneously turning on/off the reset switches RSWin a plurality of the operational circuits 8A. The reset switches RSWmay be controlled by a CPU (not shown) or the like.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2009-155188 filedin the Japan Patent Office on Jun. 30, 2009, the entire content of whichis hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1.-20. (canceled)
 21. A touch detection device comprising: a detectionsurface; driving electrodes each extending in a first direction; sensorlines each extending in a second direction that crosses the firstdirection, wherein the sensor lines are formed from types of wiringlines, which include a first sensor line and a second sensor line thathas a different length from a length of the first sensor line; a touchdetection unit that detects an electric variation generated in thesensor lines associated with touch or proximity of a detection targetobject to the detection surface, wherein the touch detection unit has anoperational circuit for generating a detection signal corresponding tothe detected electric variation at the adjacent independent sensorlines.
 22. The touch detection device according to claim 21, wherein thesensor lines are formed from M types of wiring lines that have thedifferent length for each type and are arranged in parallel to oneanother, and M sensor lines neighboring to one another are a differenttype, wherein the first sensor line has a longest length among the Msensor lines, and wherein the second sensor line has a shortest lengthamong the M sensor lines.
 23. The touch detection device according toclaim 22, wherein the M sensor lines are formed from wiring lines havinga same material, a same thickness, a same width, and different lengths,wherein each of the M sensor lines has a length which is a K multiple(where, K=1 to N) of a length L of the second sensor line having ashortest length, and wherein the operational circuit obtains thedetection signal by selecting two sensor lines including a longestsensor line from the M sensor lines, sampling two outputs from the twosensor lines at a timing corresponding to a ratio of the lengths of thetwo selected sensor lines, and performing a difference operation forsampling values.
 24. The touch detection device according to claim 23,wherein the coefficients M and N are set to
 3. 25. The touch detectiondevice according to claim 22, wherein the M sensor lines are formed fromwiring lines having a same material, a same thickness, a same width, anddifferent lengths, wherein each of the M sensor lines has a length whichis a K multiple (where, K=1 to N) of a length L of the second sensorline having a shortest length, and wherein the operational circuitobtains the detection signal by selecting two sensor lines from the Msensor lines, obtaining a difference of outputs for the two selectedsensor lines of which a ratio of lengths is set to k (where, k is anatural number equal to or larger than 2), and removing the obtaineddifference with (k−1).
 26. The touch detection device according to claim22, wherein one of the operation circuits and another operation circuitare connected to the same sensor line, and different types of sensorlines are arranged in symmetry with respect to the sensor line common tothe two operational circuits.
 27. The touch detection device accordingto claim 22, wherein the different types of M sensor lines areperiodically repeatedly arranged.
 28. The touch detection deviceaccording to claim 21, wherein the sensor lines are formed from M typesof wiring lines that have the different length for each type and arearranged in parallel to one another, wherein the first sensor line has alongest length among the M sensor lines, wherein the second sensor linehas a shortest length among the M sensor lines, wherein each of thedriving electrodes is capacitively coupled to the sensor lines, whereinthe driving electrodes are arranged in parallel, and wherein the touchdetection device further includes a scan driving unit that sequentiallyvoltage-driving (scanning) the driving electrodes from a drivingelectrode of one end to a driving electrode of the other end.
 29. Thetouch detection device according to claim 27, wherein the touchdetection unit obtains a position of the detection target object basedon the detection signal generated from the operational circuit and timeinformation synchronized with the scanning of the scan driving unit. 30.The touch detection device according to claim 22, wherein each of theoperational circuits for each of the M sensor lines that neighbor to oneanother and have a different type includes a reset switch forsimultaneously resetting electric potentials of the sensor lines in allof the operational circuits.
 31. The touch detection device according toclaim 22, further comprising a conductive layer for shielding a sensorline of a type having a shortest length out of the M sensor lines.
 32. Adisplay device having a touch sensor function, the display devicecomprising: a display surface; image signal lines; a display functionlayer that changes display of the display surface in response to signalvoltages applied to the image signal lines; driving electrodes eachextending in a first direction; sensor lines each extending in a seconddirection that crosses the first direction, wherein the sensor lines areformed from types of wiring lines, which include a first sensor line anda second sensor line that has a different length from a length of thefirst sensor line; and a touch detection unit that detects an electricvariation generated from the sensor lines in response to touch orproximity of a detection target object to the display surface, whereinthe sensor lines are formed from different types of wiring lines havinga different line capacitance due to the different length for each type,and wherein the touch detection unit includes an operational circuit forgenerating a detection signal corresponding to the detected electricvariation at the adjacent independent sensor lines.
 33. The displaydevice according to claim 32, wherein the sensor lines are formed from Mtypes of wiring lines that have the different length for each type andare arranged in parallel to one another, and M sensor lines neighboringto one another are a different type, wherein the first sensor line has alongest length among the M sensor lines, wherein the second sensor linehas a shortest length among the M sensor lines, and wherein the touchdetection unit has the operational circuit provided for each of the Msensor lines that neighbor to one another and are a different type. 34.The display device according to claim 33, wherein the M sensor lines areformed from wiring lines having a same material, a same thickness, asame width, and different lengths, wherein each of the M sensor lineshas a length which is a K multiple (where, K=1 to N) of a length L ofthe second sensor line having a shortest length, and wherein theoperational circuit obtains the detection signal by selecting two sensorlines including a longest sensor line from the M sensor lines, samplingtwo outputs from the two sensor lines at a timing corresponding to aratio of the lengths of the two selected sensor lines, and performing adifference operation for sampling values.
 35. The display deviceaccording to claim 33, wherein the sensor line having a maximum lengthout of the M sensor lines intersects with two opposite sides of aneffective display area of the display surface, and the sensor linehaving a minimum length out of the M sensor lines is disposed outsidethe effective display area.